Adhesives are made up of various components such as polymers, tackifiers, waxes and oils. Adhesive formulations based on these ingredients are susceptible to degradation. The consequences of degradation are discoloration, loss of elongation, loss of tensile strength, loss of tack and change in viscosity, molecular weight and molecular weight distribution. Degradation can be caused by prolonged exposure to sunlight. Sunlight contains invisible ultraviolet (UV) radiation with wavelengths between 290 and 400 nm. This radiation is responsible for the initiation of photodegradation.
Absorption of UV light by chromophores present in the adhesive formulation transforms the chromophores into their excited states which can undergo further undesired reactions. Some polymers contain strongly absorbing chromophores as a major part of their structures. Other polymers contain unintentional impurities such as ketones and hydroperoxide moieties and catalyst residues which act as chromophores. Absorption of UV radiation by these chromophores eventually results in bond cleavage, chain scission and/or crosslinking reactions.
Photostabilization of adhesives can be achieved by the addition of UV absorbers which convert the absorbed energy into harmless heat. An ideal UV absorber should be extremely photostable and have strong absorption over the UV range from 290 to 400 nm, but particularly the range of 350 to 400 nm. Classes of UV absorbers include the salicylates, cyanoacrylates, malonates, oxanilides, benzophenones, s-tiazines and benzotriazoles.
Salicylates, cyanoacrylates, malonates and oxanilides absorb UV light primarily at the lower wavelengths of the UV range. These compounds have little to no absorption in the range of 350 to 400 nm which make them unsuitable for the instant applications. Benzophenones absorb over the lower half of the UV range, and they tend to be prone to yellowing upon light exposure due to photodegradation. Recently, it has been shown photochemically that benzophenones decompose prematurely in ethylene-vinyl acetate encapsulants which lead to the production of polyenic chromophores. This color generation from light yellow to brown is not only highly undesirable and unsightly in adhesive systems, but also can results in a loss of adhesive properties. By contrast, selected benzotriazole UV absorbers are particularly useful because of their increased photostability.
Some polymers such as polycarbonates, polyesters and aromatic polyurethanes contain strongly absorbing chromophores as a major and integral part of their structures. Poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN) are particular examples the latter of which absorbs into the red UV region and especially need red-shifted benzotriazoles for UV protection. U.S. Pat. No. 5,294,473 and WO 98/34981 teach the use of coatings containing UV absorbers including some benzotriazoles in stabilizing PEN films. Adding an adhesive UV screening layer containing the benzotriazoles, especially those described in the instant invention, further protects such polymers in multilayered constructions and articles.
The description, preparation and uses of the 2H-benzotriazole UV absorbers are described in U.S. Pat. Nos. 3,004,896; 3,055,896; 3,072,585; 3,074,910; 3,189,615; 3,230,194; 4,127,586; 4,226,763; 4,278,589; 4,315,848; 4,383,863; 4,675,352; 4,681,905 and 4,853,471.
Although benzotriazoles with just hydrogen at the 5-position of the benzo ring are photostable and useful in adhesive formulations, they lack a red-shifted absorbance toward longer UV wavelengths which would be most useful in giving added protection to the substrates. U.S. Pat. Nos. 5,319,091 and 5,410,071 described the preparation of benzotriazoles substituted at the 5-position of the benzo ring with alkyl- or aryl-sulfonyl moieties. It is taught in U.S. Pat. No. 5,280,124 that by introducing a higher alkyl or aryl sulfoxide or sulfone at the 5-position of the benzo ring of the benzotriazole, the resulting benzotriazole exhibits enhanced absorption in the near visible range (over 350 nm). Such sulfone substituted products were shown to be useful in automotive coatings applications. Copending patent applications Ser. Nos. 08/961,127 and 09/234,880 teach that an electron withdrawing moiety at the 5-position of the benzo ring of the benzotriazole is advantageous for similar reasons. Additionally, these copending patent applications teach that such an electron withdrawing group dramatically increases the photostability of these benzotriazole UV absorbers in automotive coatings. Quite surprisingly, these red-shifted benzotriazoles are amazingly soluble in adhesives making them especially well-suited for the instant applications.
It is known in the art that the concomitant use of a hindered amine light stabilizer with a UV absorber such as a benzotriazole provides excellent stabilization in many polymer compositions as summarized by G. Berner and M. Rembold, "New Light Stabilizers for High Solids Coatings", Organic Coatings and Science and Technology, Vol. 6, Dekkar, New York, pp 55-85.
The benzotriazole UV absorbers represent a special class of commercial UV absorbers as described above. Only a few references refer to substitution on the benzo ring by an aryl or alkyl sulfoxide or sulfonyl moiety.
U.S. Pat. No. 3,218,332 discloses benzotriazoles substituted at the 5-position of the benzo ring by a lower alkyl sulfonyl moiety. However, this patent deals with putting reactable groups, namely alkenyl groups, at the 3-position on the phenyl ring and is of little relevance to the instant application. U.S. Pat. Nos. 5,268,450 and 5,319,091 disclose polymer compositions and a process for the production of substituted aryl thio and aryl sulfonyl benzotriazoles which are covalently bound to polymers, such as poly(phenylene sulfide), RYTON.RTM., Phillips Petroleum. U.S. Pat. No. 5,280,124 discloses benzotriazoles with only higher alkyl or aryl sulfonyl or sulfonyl moieties at the 5-position of the benzo ring which are useful for protecting thermoset automotive coatings. The copending patent applications mentioned above teach the use of certain electron withdrawing groups including some sulfonyl groups at the 5-position of the benzo ring for the stabilization of automotive coatings.
Japanese Patent No. 92-352228 discloses the use of 5-ethylsulfonyl benzotriazoles with the 3-position of the phenyl ring being unsubstituted or substituted by methyl for the UV protection of dust proof poly(vinyl chloride) resin films. These compounds when studied in the instant adhesive compositions were found to be quite insoluble and totally useless for the instant adhesive compositions. By contrast, when a tertiary alkyl group is inserted at the 3-position of the phenyl ring, the solubility of the thus substituted benzotriazole in adhesive composition is surprisingly enhanced.
The instant compounds exhibit enhanced broadened absorption characteristics particularly in the long wavelength UV region (over 350 nm) when compared with compounds of the prior art. Additionally, the instant compounds have surprising and unexpectedly high solubility in adhesives making them especially well suited for use in adhesive formulations.
The effect of UV light on laminated articles that are exposed to the sun or other sources of UV light are of great concern to the manufacturers of such articles. Over time, constant or repeated exposure to UV light can result in dye and/or pigment fade for dyes and/or pigments used in such articles and in the degradation or breakdown of the adhesives, polymers or other materials used in the construction of the articles. The aforementioned fading and degradation shorten the useful life of the articles in question, making protection from UV light exposure an issue of great importance to the manufacturers of such articles.
Molecules known as UV absorbers are generally known in the art. However, due to the differences discussed above between the various UV absorber classes, it is the benzotriazoles and articles containing them which will be discussed here. Due to the incompatibility and low solubility of certain benzotriazoles, a need exists for selected benzotriazoles that are highly soluble and which would provide added protection in the 350 to 400 nm region of the ultraviolet. T. Nagashima et al., J. Non-Cryst. Solids, 178 (1994), 182, report "Recently ultraviolet light (UV) shielding glass, which is UV absorbing over the range of long wavelengths (320-400 nm) to avoid sunburn effects, has become an important issue because of the possible hazard of skin cancer due to depletion of the ozone layer."
In addition, articles which incorporate the selected benzotriazoles of the instant invention are useful in protecting interior structures, textiles and fabrics from UV induced photodegradation such as in automotive applications.
International application WO 97/32225 describes the use of PEN films having reflective and polarizing elements for use as optical films.
U.S. Pat. No. 5,770,114 discloses stabilized compositions containing soluble benzotriazoles that are used in electrochromic devices. However, these benzotriazoles lack the red-shifted absorption at the 350 to 400 nm region.
Articles which would benefit from the incorporation of the instant, highly soluble, photostable and red-shifted benzotriazoles include, but are not limited to:
(a) Retroreflective Sheets and Signs and Conformable Marketing Sheets as seen in WO 97/42261; and U.S. Pat. No. 5,387,458 which is incorporated herein by reference; PA1 (b) Solar Control Films of Various Construction as seen in British 2,012,668; European 355,962; and U.S. Pat. Nos. 3,290,203; 3,681,179; 3,776,805 and 4,095,013 which are incorporated herein by reference; PA1 (c) Corrosion Resistant Silver Mirrors and Solar Reflectors as seen in U.S. Pat. No. 4,645,714 which is incorporated herein by reference; PA1 (d) Reflective Print Labels as seen in U.S. Pat. No. 5,564,843 which is incorporated herein by reference; PA1 (e) UV Absorbing Glasses and Glass Coatings as seen in U.S. Pat. Nos. 5,372,889; 5,426,204; 5,683,804 and 5,618,626 which are incorporated herein by reference; PA1 (f) Electrochromic Devices as seen in European 752,612 Al; and U.S. Pat. Nos. 5,239,406; 5,523,877 and 5,770,114 which are incorporated herein by reference; PA1 (g) Films/Glazings as seen in WO 92/01557; Japanese Nos. 75-33286; 93-143668; 95-3217 and 96-143831; and U.S. Pat. No. 5,643,676 which is incorporated herein by reference; PA1 (h) Windscreens and Intermediate Layers as seen in Japanese Nos. 80-40018; 90-192118; 90-335037; 90-335038; 92-110128 and 94-127591; and U.S. Pat. No. 5,618,863 which is incorporated herein by reference; and PA1 (i) Optical Films as seen in WO 97/32225; and U.S. Pat. Nos. 4,871,784 and 5,217,794 which are incorporated herein by reference. PA1 (a) an adhesive; and PA1 (b) an effective stabilizing amount of a highly soluble, red-shifted, photostable benzotriazole. PA1 when n is 2, E.sub.5 is one of divalent radicals --O--E.sub.9 --O-- or --N(E.sub.11)--E.sub.10 --N(E.sub.11)--, PA1 with the proviso that formula I does not represent 5-ethylsulfonyl-2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole; 5-fluoro-2-(2-hydroxy-3-a-cumyl-5-tert-octylphenyl)-2H-benzotriazole; 5-fluoro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benzotriazole ; 5-chloro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benzotriazole ; 5-chloro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benzotriazole ; 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; or 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole; and PA1 with the further proviso that the benzotiazole of formula I, II or mH exhibits enhanced durability and low loss of absorbance when exposed to actinic radiation as witnessed by an absorbance loss of less than 0.5 absorbance units after exposure for 893 hours or less than 0.8 absorbance units after exposure for 1338 hours in a Xenon Arc Weather-Ometer. PA1 is a compound of formula I wherein, PA1 with the proviso that formula I does not represent 5-ethylsulfonyl-2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole; 5-fluoro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benzotriazole ; 5-fluoro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benzotriazole ; 5-chloro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benzotriazole ; 5-chloro-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benzotiiazole ; 5-chloro-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; or 5-chloro-2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-2H-benzotriazole; and PA1 with the further proviso that the benzotriazole of formula I exhibits enhanced durability and low loss of absorbance when exposed to actinic radiation as witnessed by an absorbance loss of less than 0.5 absorbance units after exposure for 893 hours or less than 0.8 absorbance units after exposure for 1338 hours in a Xenon Arc Weather-Ometer. PA1 is a compound of formula I wherein, PA1 (a) 5-trifluoromethyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benz o-triazole; PA1 (b) 5-trifluoromethyl-2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole; PA1 (c) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole; PA1 (d) 2,2'-methylene-bis[6-(5-trifluoromethyl-2H-benzotriazol-2-yl)-4-tert-octyl -phenol]; PA1 (e) methylene-2-[4-tert-octyl-6-(2H-benzotriazol-2-yl)phenol]2'-[4-tert-octyl- 6-(5-trifluoromethyl-2H-benzotriazol-2-yl)phenol]; PA1 (f) 3-(5-trifluoromethyl-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxy-hydrocin namic acid; PA1 (g) methyl 3-(5-trifluoromethyl-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxy-hydrocin namate; PA1 (h) isooctyl 3-(5-trifluoromethyl-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxy-hydrocin namate; PA1 (i) 5-trifluoromethyl-2-[2-hydroxy-5-(3-hydroxypropyl)phenyl]-2H-benzotriazole ; PA1 (j) 5-butylsulfonyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benzot riazole; PA1 (k) 5-octylsulfonyl-2-(2-hydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazole; PA1 (l) 5-dodecylsulfonyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; PA1 (m) 5-octylsulfonyl-2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole; PA1 (n) 5-trifluorometbyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benz o-triazole; PA1 (o) 5-trifluoromethyl-2-(2-hydroxy-3-.alpha.-cumyl-5-nonylphenyl)-2H-benzotria zole; PA1 (p) 5-trifluoromethyl-2-[2-hydroxy-3-.alpha.-cumyl-5-(2-hydroxyethyl)phenyl]-2 H-benzotriazole; PA1 (q) 5-trifluoromethyl-2-[2-hydroxy-3-.alpha.-cumyl-5-(3-hydroxypropyl)phenyl]- 2H-benzotriazole; PA1 (r) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-tert-amylphenyl)-2H-benzotriazole; PA1 (s) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; PA1 (t) 5-trifluoromethyl-2-(2-hydroxy-3-dodecyl-5-methylphenyl)-2H-benzotriazole; PA1 (u) 5-trifluoromethyl-2-[2-hydroxy-3-tert-butyl-5-(3-hydroxypropyl)phenyl)-2H- benzotriazole; PA1 (v) 5-trifluoromethyl-2-[2-bydroxy-3-tert-butyl-5-(2-bydroxyethyl)phenyl]-2H-b enzotriazole; PA1 (w) 5-trifluoromethyl-2-[2-hydroxy-5-(2-hydroxyethyl)phenyl]-2H-benzotriazole; PA1 (x) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazol e; PA1 (y) 5-fluoro-2-(2-bydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazole; PA1 (z) 5-butylsulfonyl-2-(2-hydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazole; PA1 (aa) 5-butylsulfonyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; PA1 (bb) 5-butylsulfonyl-2-(2-bydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole; PA1 (cc) 5-phenylsulfonyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; and PA1 (dd) 5-chloro-2-(2-hydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazole. PA1 (a) 5-trifluoromethyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-octylphenyl)-2H-benz o-triazole; PA1 (b) 5-trifluoromethyl-2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole; PA1 (c) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-tert-octylphenyl)-2H-benzotriazole; PA1 (g) methyl 3-(5-trifluoromethyl-2H-benzotriazol-2-yl)-5-tert-butyl-4-hydroxy-hydrocin namate; PA1 (j) 5-butylsulfonyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tent-octylphenyl)-2H-benzot riazole; PA1 (n) 5-trifluoromethyl-2-(2-hydroxy-3-.alpha.-cumyl-5-tert-butylphenyl)-2H-benz o-triazole; PA1 (s) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; PA1 (x) 5-trifluoromethyl-2-(2-hydroxy-3,5-di-.alpha.-cumylphenyl)-2H-benzotriazol e; PA1 (aa) 5-butylsulfonyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole; and PA1 (cc) 5-phenylsulfonyl-2-(2-hydroxy-3,5-di-tert-butylphenyl)-2H-benzotriazole. PA1 (a) Retroreflective Sheets and Signs and Conformable Marketing Sheets; PA1 (b) Solar Control Films of Various Construction; PA1 (c) Corrosion Resistant Silver Mirrors and Solar Reflectors; PA1 (d) Reflective Print Labels; PA1 (e) UV Absorbing Glasses and Glass Coatings; PA1 (f) Electrochromic Devices; PA1 (g) Films/Glazings; PA1 (h) Windscreens and Intermediate Layers; and PA1 (i) Optical Films. PA1 (a) Retroreflective Sheets and Signs and Conformable Marketing Sheets; PA1 (b) Solar Control Films of Various Construction; PA1 (e) UV Absorbing Glasses and Glass Coatings; PA1 (g) Films/Glazings; and PA1 (h) Windscreens and Intermediate Layers. PA1 (b) Solar Control Films of Various Construction; or PA1 (h) Windscreens and Intermediate Layers. PA1 (i) Pressure Sensitive Adhesives; PA1 (ii) Rubber-Based Adhesives; PA1 (iii) Solvent and/or Emulsion Based Adhesives; PA1 (iv) Hot Melt Adhesives; and PA1 (v) Natural Product Based Adhesives. PA1 (i) Polyurethanes; PA1 (ii) Polyacrylics; PA1 (iii) Epoxys; PA1 (iv) Phenolics; PA1 (v) Polyimides; PA1 (vi) Poly(vinyl butyral); PA1 (vii) Polycyanoacrylates; PA1 (viii) Polyacrylates; PA1 (ix) Ethylene/acrylic acid copolymers and their salts (ionomers); PA1 (x) Silicon polymers; PA1 (xi) Poly(ethylenelvinyl acetate); PA1 (xii) Atatic polypropylene; PA1 (xiii) Styrene-diene copolymers; PA1 (xiv) Polyamides; PA1 (xv) Hydroxyl-terminated polybutadiene; PA1 (xvi) Polychloroprene; PA1 (xvii) Poly(vinyl acetate); PA1 (xviii) Carboxylated styrene/butadiene copolymers; PA1 (xix) Poly(vinyl alcohol); and PA1 (xx) Polyesters. PA1 (1) polyolefins; PA1 (2) mixtures of polyolefins; PA1 (3) copolymers of monoolefins and diolefins or other vinyl monomers; PA1 (4) polystyrene, poly(p-methylstyrene) or poly(.alpha.-methylstyrene); PA1 (5) copolymers of styrene or .alpha.-methylstyrene with dienes or acrylic derivative; PA1 (6) graft copolymers of styrene or .alpha.-methylstyrene; PA1 (7) halogen containing polymers; PA1 (8) polymers derived from .alpha.,.beta.-unsaturated acids and derivatives thereof; PA1 (9) copolymers of monomers of (8) with each other or other unsaturated monomers; PA1 (10) polymers derived from unsaturated alcohols and amines or the acyl derivatives or acetals thereof; PA1 (11) polyacetals such as polyoxymethylene and those polyoxymethylenes which contain ethylene oxide as a comonomer, polyacetals modified with thermoplastic polyurethanes, acrylates or MBS; PA1 (12) polyurethanes; PA1 (13) polyamides and copolyamides from diamines and dicarboxylic acids and/or from aminocarboxylic acids or the corresponding lactams; PA1 (14) polyureas or polyimides; PA1 (15) polyesters derived from dicarboxylic acids and diols and/or from hydroxycarboxylic acids or the corresponding lactones, especially poly(ethylene terephthalate) (PET) and poly(ethylene 2,6-naphthalenedicarboxylate) (PEN); PA1 (16) polycarbonates and polyester carbonates; PA1 (17) polysulfones and polyether sulfones; PA1 (18) crosslinked polymers derived from aldehydes on the one hand and phenols, ureas and melamines on the other hand; PA1 (19) unsaturated polyester resins derived from copolyesters of saturated and unsaturated dicarboxylic acids with polyhydric alcohols and vinyl compounds as crosslinking agents; PA1 (20) crosslinkable acrylic resins derived from substituted acrylates; PA1 (21) blends of the aforementioned polymers; PA1 (22) polysiloxanes; PA1 (23) polyketimines in combination with unsaturated acrylic polyacetoacetate resins or with unsaturated acrylic resins; PA1 (24) radiation curable compositions containing etbylenically unsaturated monomers or oligomers and a polyunsaturated aliphatic oligomer; and PA1 (25) ionomers (copolymers of ethylene/acrylic acid and their salts). PA1 Preferably the adhesive component (a) is a resin selected from the group consisting of PA1 poly(vinyl butyral), ethylene/vinyl acetate copolymers, polyacrylics, polyacrylates, natural rubber, polycyanoacrylates, poly(vinyl alcohol), styrene/butadiene rubber, phenolics, urea-formaldehyde polymers, epoxy resins, vinyl polymers, polyamides, polyurethanes, polyesters and styrene block copolymers. PA1 poly(vinyl butyral), ethylene/vinyl acetate copolymers, polyacrylics, polyacrylates, natural rubber, polycyanoacrylates, poly(vinyl alcohol), styrenelbutadiene rubber, phenolics, vinyl polymers, polyurethanes and styrene block copolymers.